well, i took a stab at it, but i didn't have much data to test against, so i made some up. this processes the log file line by line, so it doesn't use as much memory, and only passes through the file once, reading and processing in the same step. it tests the first eight characters of each line (the date,) against a predefined value, $date. if this condition holds, the line is printed, in my example, to the screen.

in order to use this, you'll have to change the DATA handle to LOG, and change print ; to print LOGFILE;

#!/usr/local/bin/perl -w
use strict;

my $date = '20020111';

while( <DATA> ) {
    # ignore lines until the first eight characters of the line are 
    # greater than or equal to $date
    next unless( substr($_, 0, 8) >= $date );
    print ;
}

__DATA__
20020109 164741    892 26,212 Directories  52,846 Files (805.49 MB) Ba
+cked Up a
20020110 164741    892 26,212 Directories  52,846 Files (805.49 MB) Ba
+cked Up b
20020111 164741    892 26,212 Directories  52,846 Files (805.49 MB) Ba
+cked Up c
20020111 164741    892 26,212 Directories  52,846 Files (805.49 MB) Ba
+cked Up x
20020112 164741    892 26,212 Directories  52,846 Files (805.49 MB) Ba
+cked Up y
20020112 164742    892 26,212 Directories  52,846 Files (805.49 MB) Ba
+cked Up z
20020113 164741    892 26,212 Directories  52,846 Files (805.49 MB) Ba
+cked Up 1
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~Particle